Restoring erectile function by combined treatment with JNK inhibitor and HDAC inhibitor in a rat model of cavernous nerve injury

Abstract

Background:The main pathophysiologic conditions of erectile dysfunction (ED) after radical prostatectomy are considered to be corporal fibrosis and apoptosis induced by cavernosal nerve (CN) injury. Objectives:In a rat model of CN crush injury (CNCI), we investigated whether combination treatment with JNK inhibitor (JNKi), SP600125, and HDAC inhibitor (HDACi), suberoylanilide-hydroxamic-7 acid (SAHA), for 2 weeks after CNCI would restore erectile function by suppressing fibrosis and apoptosis through normalization of JNK and HDAC pathways. Materials and methods:Seventy 12-week-old rats were randomly divided into five groups: Sham surgery, CNCI alone, CNCI treated with daily intraperitoneal injection of 10 mg/kg JNKi, CNCI treated with daily oral administration of 25.0 mg/kg HDACi, and CNCI daily treated with a combination. Two weeks after CNCI, we investigated the erectile response to electrostimulation and conducted histological staining, caspase-3 activity assay, and western blot analysis.Results: CNCI alone resulted in significantly reduced intracavernosal pressure/mean arterial pressure (MAP) and area under the curve/MAP, decreased smooth muscle (SM)/collagen ratio and SM content, higher caspase-3 activity, and increased protein levels of total HDAC3, transforming growth factor (TGF)-β, fibronectin, and c-Jun phosphorylation, compared with the Sham surgery. The CNCI groups exposed to JNKi, HDACi or both showed improvements in erectile-responses and SM/collagen ratio, compared to the CNCI alone. The combined treatment showed additional improvement in erectile responses at 1.0V stimulation and in SM/collagen ratio compared to the single agent treatment. SM content, caspase-3 activity, and c-Jun phosphorylation improved in the two CNCI groups exposed to JNKi. The two CNCI groups exposed to HDACi showed normalization of protein levels of HDAC3, fibronectin, and TGF-β. Discussion and conclusions:The combined administration of JNKi and HDACi during the acute phase after CNCI in rats can preserve ED by suppressing cavernosal fibrosis and apoptosis by normalizing the HDAC/TGF-β and JNK pathways.